My best friend is acting terrible because she likes my crush (I like him first and know him better) and he told her he liked me not her?

So this is how this mess started grab your popcorn. So a year or so ago a new guy came to our school (Boarding school) and he was smart, funny, sweet, kind, athletic and artisitic, and basically perfect. I liked him after we talked the first time, but my best friend started liking him AFTER and she tries to get him to notice him but he already likes me and I like him and anyway she's bee acting mean to me every time he walks into a room and she starts being all OMFG! Your sooo stupid *cue the giggling* twirls her hair bats her eyelashes and he turns to me and says um we have detention and he feels awkward around her and he told me already he likes me and not her... what do I do? And she just acts mean to me all the time ditches me and has dumped for guys before I'm just sick of her shit you know?